The latest threat to global health is the ongoing outbreak of the respiratory disease named Coronavirus Disease 2019 (Covid-19). Covid-19 is highly transmissible, causes relatively high mortality, and has spread globally in our highly interconnected world. As of 4/26/2020, in the US alone there were 963,168 confirmed COVD-19 cases and 54,614 reported deaths due to COVID-19, and the curve demonstrating cumulative cases shows no evidence of a plateau. The case-fatality rate in the US is currently ~5%, and there is emerging evidence that the elderly and those with underlying comorbidities are at higher risk of succumbing to COVID-19-related complications. Importantly, there is no information about susceptibility to this infection among other vulnerable populations, such as those with prolonged immune suppression after blood or marrow transplantation (BMT). BMT survivors are likely at higher risk for COVID-19 infection that the general population for the following reasons: i) as part of the conditioning for BMT, patients are exposed to high doses of chemotherapy and radiation; ii) BMT has been increasingly offered to older adults and BMT survivors are aging; iii) BMT survivors are at a higher risk of comorbidities (diabetes, hypertension, coronary artery disease, and heart failure); and iv) ~40% of the allogeneic BMT recipients develop chronic graft versus host disease (GvHD), and receive immune suppressive therapy to manage the GvHD for prolonged periods of time. The risk of COVID-19 infection and of COVID-19 infection-related complications as well as case-fatality rate in BMT survivors are not known. The contribution of comorbidities to COVID-related complications in BMT survivors is also unknown. We will address these gaps using a large cohort of allogeneic BMT survivors (n=2,060) who have already participated in BMTSS- 2 (parent study U01CA213140, PI, Bhatia). These patients were transplanted between 1974 and 2014, at one of 3 participating sites (UAB, COH or UMN) and survival of ?2y after BMT. As a result of their participation, we now have information on their sociodemographics, clinical characteristics and burden of morbidity. We have also enrolled a cohort of 1,150 non-cancer individuals to serve as a comparison group. We will use this rich resource to A) Describe the risk of COVID-19 infection in allogeneic BMT survivors compared to controls; B) Among participants with COVID-19 infections, compare the prevalence of severe complications in BMTSS-2 survivors with controls; C) Describe the prevalence of financial and psychosocial distress among BMT recipients compared to the controls; D) Identify BMT recipients at highest risk for COVID-19 infection and severe complications. This cohort will represent the largest and most comprehensive attempt at examining the health and wellbeing of BMT recipients during the COVID-19 pandemic. Findings from this study will have direct relevance for prevention from COVID-19 infection of not only the high risk BMT recipients, but also other individuals with a compromised immune system.